1. Field of the Invention
The present invention relates to a mobile communication system with transmitting systems with different outputting power.
2. Description of the Related Art
A Personal Handy-phone System (PHS), formerly known as Personal Handy Phone (PHP), employs a four-channel multiplex TDMA (Time Division Multiple Access)xe2x80x94TDD (Time Division Duplex) method. The four-channel TDMA method implies that four signals are arranged in time series (four bursts). The cell station can communicate with a maximum of four personal mobile stations by using the four-channel TDMA method.
In a mobile communicating system such as PHS, the apparatus for the cell station (CS) is required to be miniaturized, of light weight and low power consumption, since the apparatus of the cell station services an infrastructure. Especially, flexibility in the manner of installation of the cell station is extremely important for a PHS system needing a large number of cell stations. From this viewpoint, the apparatus of the cell station which is made smaller and lighter is required. The cell station is installed in various manners, and the cell station is installed on a public telephone box, a telephone pole, a wall of a building, a housetop and the like in the outdoors, and installed on a ceiling, a public telephone base and the like in an underground market, an underpass and a building.
When a cell station having a plurality of channels has a plurality of transmitters, output powers of the respective transmitters are set to values identical to each other. Thus, the power consumption of the cell station is increased in proportion to the number of transmitters which the cell station has (by integer multiples).
Especially when the cell station has a high-power outputting transmitter, the high-power outputting transmitter generates a large amount of heat. As a result, the high-power outputting transmitter requires increasing the number of fins and making a surface area wider to improve the heat radiation as the solution. This results in a problem that the apparatus of the cell station is made large in size and heavy. Hence, the cell station becomes more expensive to manufacture and further the flexibility in the manner of installation is impaired.
Moreover, a high-power outputting power amplifier is expensive in itself. Thus, if the number of high-power outputting transmitters is increased, the cost of the cell station is correspondingly made largely expensive.
Therefore, it is necessary to develop a small cell station apparatus in which the heat generation amount is dropped and to reduce the cost while the quality of communication service is kept in a conventional level.
In addition, the following techniques have been traditionally provided, with regard to the mobile communicating method and the cell station.
Japanese Laid-Open Patent Application (JP-A-Showa 62-82731) describes the following conventional mobile communicating method. When a plurality of kinds of personal mobile stations whose transmission powers are different from each other are in one service area (for example, in an automobile telephone, a personal mobile station which is fixed in a vehicle and has a large transmission power, and a personal mobile station having a small transmission power which is portable after a user gets off), a plurality of slave cell stations having small transmission powers are installed in a service area of a master cell station having a large transmission power.
The above-mentioned mobile communication method needs a plurality of master and slave cell stations in the one service area and the above-mentioned mobile communication method becomes expensive. Also, the above-mentioned mobile communication method has the premise that there are a plurality of kinds of personal mobile stations whose transmission powers are different from each other. Thus, the above-mentioned problems can not be solved.
Japanese Laid-Open Patent Application (JP-A-Heisei 7-177570) describes the following radio telephone apparatus. This radio telephone apparatus has both functions of a cellular mode and a PHP (Personal HandyPhone) mode in a single radio telephone apparatus and can switch between incoming and outgoing calls as a cellular type radio telephone apparatus if a user is not located within a PHP service area, or as a PHP type radio telephone apparatus if the user is located within the PHP service area.
The above-mentioned radio telephone apparatus has only a technique of giving the two-mode function to the single apparatus as the personal mobile station and then switching between the modes in accordance with a reception field strength. Thus this can not solve the problem of miniaturizing the apparatus of the cell station, decreasing the cost and reducing the heat generation.
Japanese Laid-Open Patent Application (JP-A-Heisei 10-23498) describes the following radio cell station, subscriber apparatus and operation method. This conventional example is provided with: a plurality of cell stations each containing a plurality of subscriber apparatuses; a hybrid section for integrating and treating signals, which are transmitted and received by the plurality of cell stations, between it and a single antenna; and a multiplexing/separating section for integrating and treating signals which are transmitted and received between the plurality of cell stations and an existing network, with regard to WLL (Wireless Local Loop) using PHS.
Japanese,Laid-Open Patent Application (JP-A-Heisei 5-292010) describes the following method and apparatus for assigning a radio channel. A radio zone is divided into concentric circles of the same area. A cell station is positioned at a center of each of the concentric circles. The number of cell stations is equal to the number of channels which can be used in a whole system. A channel is assigned to each region. In a case of an occurrence of a channel assignment request, the corresponding channel and the vicinity are preferentially assigned to the region at which the personal mobile station is located.
Japanese Laid-Open Patent Application (JP-A-Heisei 10-51380) describes the following CDMA (Code Division Multiple Access) system, an apparatus for controlling its transmission power and a DBF antenna. A side of a cell station has a non-directional antenna and a directional antenna. A non-directional antenna section has a transmitting/receiving unit for transmitting to M personal mobile stations. Each of them has a power measuring unit and a comparator with a first standard value. A directional antenna section has a transmitting/receiving unit so as to be connected to (Nxe2x88x92M) personal mobile stations. Each of them has a power measuring unit and a comparator with a second standard value. Those two standard values are established in accordance with a ratio of a reception power to an interference power density.
Japanese Laid-Open Patent Application (JP-A-Heisei 6-311089) describes the following method for again using a frequency. A cell station has a plurality of call channels which are divided into an interior area call channel apparatus group and an exterior area call channel apparatus group. A service area of the cell station is logically divided into an interior area and an exterior area on a concentric circle in accordance with a predicted traffic. A minimum desirable wave level in an interior area call channel apparatus is kept higher than a minimum desirable wave level in an exterior area call channel apparatus.
Japanese Laid-Open Patent Application (JP-A-Heisei 4-47722) describes the following method for controlling a radio assignment in a mobile communication. At first, in a plurality of cell stations installed in a service area, the individual cell station has a first antenna for targeting a first radio zone and a second antenna for targeting a second radio zone. Here, the second radio zone is narrower in region than the first radio zone. Also, a vertical in-plane directivity of the second antenna is facing further downward from that of the first antenna. Each cell station is designed to select an antenna used for communicating with a mobile station, in accordance with the relationship of magnitude between reception levels at both the antennas in an electric wave from the mobile machine.
Japanese Laid-Open Patent Application (JP-A-Heisei 8-228375) describes the following method for installing a radio channel. An inside cell base station and an outside cell base station are located at respective centers of an outside cell and an inside cell. Here, the inside cell base station carries out a radio communication with a mobile machine within the inside cell. The outside cell base station carries out a radio communication with a mobile station within the outside cell. A service area is divided by a plurality of outside cells. The inside cell whose diameter is thinner than that of the outside cell and whose center is located at a position substantially common to a central position of the outside cell is provided at each of the plurality of outside cells. A channel control circuit is designed such that utilization channels of the inside cell and the outside cell are installed at the optimal channels so as not to respectively bring about a third dimensional mutual modulation in the inside cell base station and the outside cell base station.
The present invention has been made to solve the above-explained problems.
Therefore, an object of the present invention is to provide a radio cell station apparatus which generates less heat, has a small size and is provided at a low cost.
Another object of the present invention is to provide a PHS public cell station apparatus which generates less heat, has a small size and is provided at a low cost.
Still another object of the present invention is to provide a mobile communicating method in which a radio cell station apparatus generates less heat, has a small size and is provided at a low cost.
Especially when the cell station has a high-power outputting transmitter, the high-power outputting transmitter generates a large amount of heat. As a result, the high-power outputting transmitter requires increasing the number of fins and making a surface area wider to improve the heat radiation as the solution. This results in a porblem that the apparatus of the cell station is made large in size and heavy. Hence, the cell station becomes more expensive to maufacture and further the flexibility in the manner of installation is impaired.
In the radio cell station, the plurality of transmitters may output the signals with respective different transmission powers.
In the radio cell station, the positioning data may correspond to an electric field strength of the transmission signal outputted by the radio cell station apparatus and received by the personal mobile station.
The radio cell station may further include a single body, such that the plurality of transmitters are accommodated inside the body.
In the radio cell station, the plurality of transmitters may include a first transmitter outputting the transmission signal at a rated power, and a second transmitter outputting the transmission signal at a power lower than the rated power.
In the radio cell station apparatus, the controller may include a distance measuring section measuring a distance from the radio cell station apparatus to the personal mobile station, and a transmitter selecting section selecting one of the first transmitter and the second transmitter as the activated transmitter based on the distance measured by the distance measuring section.
In the radio cell station apparatus, the controller may include a transmitter selecting section selecting any one of the first transmitter and the second transmitter as the activated transmitter based on a field strength of the transmission signal which is outputted by the radio cell station apparatus and are received by the personal mobile station, a data indicating the electric field strength being transmitted to the radio cell station.
In the radio cell station apparatus, a control channel used to control outgoing/incoming call may be assigned to a first signal outputted from the first transmitter.
In the radio cell station apparatus, a plurality of communication channels may be respectively assigned to a first signal outputted from the first transmitter and a second signal outputted from the second transmitter, and a first number of the communication channels assigned to the first signal and a second number of the communication channels assigned to the second signal may be respectively defined based on respective service areas determined by respective transmission powers of the first signal and the second signal.
In the radio cell station apparatus, a first signal outputted from the first transmitter may include a first frame assigned to four transmission slots, in which a control channel controlling outgoing/incoming calls and three communication channels are assigned to the four transmission slots of the first frame, and a second signal outputted from the second transmitter may include a second frame including four transmission slots, the three communication channels are assigned to three of the four transmission slots of the second frame.
In order to achieve another aspect of the present invention, the present invention provides a mobile communication method including:
(a) providing a radio cell station having a first transmitter outputting a first transmission signal at a first power and a second transmitter outputting a second transmission signal at a second power lower than the first power;
(b) obtaining data corresponding to a distance between the radio cell station and a personal station communicating with the radio cell station, and judging whether or not the data exceeds a pre-determined value;
(c) outputting the second transmission signal from the second transmitter of the radio cell station to the personal mobile station, when the data exceeds the pre-determined value; and
(d) outputting the first transmission signal from the first transmitter of the radio cell station to the personal mobile station, when the data does not exceed the pre-determined value.
In the mobile communication method, the (c) outputting may further include
(e) outputting the first transmission signal from the first transmitter of the radio cell station to the personal mobile station, when the data exceeds the pre-determined value and communication channels assigned to the second transmission signal outputted by the second transmitter are all busy, in which the communication channels are composed of the pre-determined number of transmission slots assigned to the second transmission signal.
In the mobile communication method, the data may be determined based on a field strength of the transmission signal which is outputted by the radio cell station and is received by the personal mobile station.
In the mobile communication method, a control channel used by controlling the outgoing/incoming call may be assigned to the first transmission signal outputted by the first transmitter. In order to achieve still another aspect of the present invention, the present invention provides
a PHS public cell station apparatus including a single body, and a plurality of transmitters contained in the single body, in which the plurality of transmitters include a first transmitter which outputs a first transmission signal at a first power in which a plurality of slots assigned to a first frame in the first transmission signal are composed of a control channel used by controlling outgoing/incoming call and a plurality of the communication channels capable of communicating a plurality of mobile station at the same time, and a second transmitter which outputs a second transmission signal at a second power lower than the first power in which a plurality of slots assigned to a second frame in the second transmission signal are composed of a plurality of the communication channels.
In the PHS public cell station apparatus, the first frame may be provided with one slot assigned to the control channel and three slots assigned to the communication channels, and the second frame may be provided with three slots assigned to the communication channels.
The PHS public cell station apparatus may further include a controller selectively activating one of the first transmitter or second transmitter based on positioning data corresponding to a position of the personal mobile station such that the activated transmitter communicates with the PHS public cell station apparatus using a transmission signal.
In the PHS public cell station apparatus, the first transmitter may communicate with a personal mobile station in a first transmitting area, and the second transmitter may communicate with a personal mobile station in a second transmitting area communicating in which all of the second transmitting area is inside the first transmitting area, and the PHS public cell station apparatus may further include a controller which controls the first transmitter to be activated when a personal mobile station communicating with the PHS public cell station apparatus is inside the first transmitting area except the second transmitting area or when the personal mobile station is inside the second transmitting area and all of the communication channels of the second transmitter is assigned to another personal mobile stations, and which controls the second transmitter to be activated when the personal mobile station is inside the second transmitting area and at least one of the communication channels of the second transmitter is not assigned to another personal mobile stations.